N-methyl saccharin in formaldehydeurea molding compositions



Patented May 14, 1940 UNITED STATES PATIENT OFFICE N-METHYL SACCHARIN IN FORMALDEHYDE- UREA MOLDING COMPOSITIONS Emil n. Balz, Toledo, ohm, assignor to Plaskon Company, Incorporated, Toledo, Ohio, a corporatlon of Delaware No Drawing. Application August/8, 1938,

I Serial-No. 223,691 1 3 Claims.

time and while the article is still hot. In contrast, an article molded from a thermoplasticw composition cannot be removed from the mold. until it has cooled and thus hardened suificiently so that it does not become distorted, dented, or otherwise marred in being removed. The length of time for which a molding composition must be left in the mold is one of the factors thatdetermines the cost of articles molded from the composition. A molding composition that must be left in the mold twice as long as another composition requires about twice as much molding equipment for the same volume of production, and hot-molding equipment is expensive.

, Formaldehyde-urea molding compositions are thermosetting, but articles molded therefrom must be left in the heated mold for a short time after the composition has. actually become hard, in order that a resin of optimum properties may be produced. It has been found that curing of the resin by keeping it at the molding temperature for the proper length of time is required to bring out its optimum properties. There is of course a demand for formaldehyde-urea molding compositions that require curing for a relatively short time.

A latent accelerator in a formaldehyde-urea molding composition is an ingredient that accelerates the curing of the composition without materially impairing its stability in storage at ordinary temperatures. True latent accelerators are very rare. They may be alkaline, neutral, or so slightly acid that they do not appreciably acidify a molding composition when added there to. It is believed that they are, substances that break up or undergo molecular rearrangement to form acids, but do not do so until the molding temperature is reached. The acids so formed must be strong enough to serve as catalysts that hasten the curing of the formaldehyde-urea res- Formaldehyde-urea molding compositions contain appreciable moisture, and are frequently kept in storage for weeks at a time before being used. Many substances that might be expected to decompose or rearrange to form acids under molding conditions suffer the same-decomposition or rearrangement within a few hours after being intimately mixed with a molding composition. Moreover, the behavior of a substance 'when present as a minor ingredient in a molding composition and subjected to. molding pressures at the molding temperatures of to C. cannot be predicted from its behavior when subjected by itself to temperatures of 130 to 160 C, at atmospheric pressure. Most of the potentially acid substances that when incorporated with a molding composition do not materially affect its stability, also do not materially accelerate the curing of the composition in the mold.

A substance that materially impairs the stability of a molding composition is a highly undesirable ingredient. The manufacturer of a formaldehyde-urea molding composition must mold articles for various periods of time at various temperatures and pressures and carefully test them to determine the molding conditions and curing time required to give the desired results. 25 If a molding composition contains an ingredientthat materially impairs the stability of the composition, articles molded from the composition 7 will be inferior, not only because the composition gradually deteriorates during storage, but also because the molding conditionsrequired for producing articles with the desired properties from batches of the composition that have been stored for various periods under various conditions are indeterminate.

Although certain halogenated organic compounds that liberate hydrobromic and hydrochloric acid when heated have been known to act as latent accelerators when incorporated in formaldehyde-urea molding compositions, accelerators that liberate organic acids are preferable to accelerators that liberate strong inorganic acids. Certain organic peroxides, such as benzoyl peroxide, have been used heretofore as latent accelerators, but there are manyorganic pigments 45 that cannot be used in a molding composition containing a peroxide. I

The principal object of the invention is to provide a formaldehyde-urea molding composition 50 containing a novel latent accelerator. More spe- .cific objects and advantages are apparent from the description, which merely discloses and illustrates the invention and is not intended to impose limitations upon the claims.

tion contains N-methyl saccharin A molding composition embodying the inven- Example A formaldehydeurea molding composition containing 100- parts of cellulose impregnated with 100 parts 01a iormaldehyde-urea reaction part of N-methyl saccharin.

product is ground'in a ball' mill together with 1 The customary modifiers, such as lubricants, opacifiers and coloring matter, may also be added during the grinding. After an intimate mixture has been formed, the resulting powder is granulated or formed into pellets so that it can be conveniently inserted in a mold. The molding is performed under a suitable pressure at a temperature of about 150 C.

Various molding compositions embodying the invention may be prepared to meet various requirements.

Having described my invention, I claim: a ,1. A thermosetting molding composition comprising a formaldehyde-urea reaction product and N-methyl saccharin as a latent accelerator.

2. A formaldehyde-urea molding composition comprising about /2 per cent of N-methyl saccharin as alatent accelerator.

3. A formaldehyde-urea molding composition comprising a formaldehyde-urea reaction product, cellulosic material, and N-methyl saccharin as a latent accelerator. i

' EMIL H. BALZ. 

